Slurries Specification

Table 4-155 gives the API recommended optimum water-to-cement ratios and the resulting neat slurry specific weight (Ib/gal) and specific volume, or yield (ftVsack) for the various classes of API cements [161]. 

The most common low-specific-gravity solids used to reduce cement slurry specific weight are bentonite, diatomaceous earth, solid hydrocarbons, expanded perlite and pozzolan. It may not be possible to reduce the cement slurry specific weight enough with the above low-specific-weight materials when very weak formations are exposed. In such cases nitrogen is used to aerate the mud column above the cement slurry to assist in further decreasing the hydrostatic pressure. 

Ilmenite. This additive has a specific gravity of about 4.67. It is a mineral composed of iron, titanium and oxygen. It requires no additional water to be added to the slurry thus, it can yield slurry specific weights as high as the hematite additive. Ilmenite also has mineral effect on thickening time and compressive strength of the cement. 

Sand. Ottawa sand has a low specific gravity of about 2.63. But since no additional water is required when using this additive, it is possible to use sand to increase the cement slurry specific weight. The sand has little effect on the pumpability of the cement slurry. When set the cement will form a very hard surface. Sand used as an additive can be used to increase the specific weight of a cement slurry to as high as 18 Ib/gal. 

Metrology for monitoring slurry health has evolved from pH and density to include particle size and slurry-specific parameters such as component assay and conductivity. Other parameters mentioned earlier are occa-... 

System performance and power requirement are therefore normally graphically presented and calculated in the same way as for clear liquids. Subject to some minor corrections, a centrifugal pump will pump the same volumetric flowrate of slurry as for water through a given flow system. The pump discharge pressure and its power draw will be increased in proportion to the slurry specific gravity, as for any clear fluid of increased density. 

Disperse phase in feed slurry Specific filfrafion rafe kg m h Vacuum filfrafion Press belf filfrafion Reducfion in residual moisfure Fuei saving in downsfream dryer... 

A slurry pipeline is designed to handle flow at a pressure of 3.5 MPa (= 500 psi). The slurry specific gravity is 1.5. Determine the number of pumps to be installed in the pump station (assume a head factor of 0.83). 

Acid-Base Behavior. The relative acidity-basicity of the filler, generally determined by measuring the pH value of a slurry of a specific mass of filler in 100 mL of deionized water, can influence the behavior of a filler in some systems. For example, the curing behavior of some elastomers is sensitive to the pH value of carbon black. 

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